考虑转捩的风力机翼型动态失速数值模拟

以风力机专用翼型的动态失速为对象,采用一种基于流场当地变量的Gamma-Theta转捩模型配合SSTk-ω湍流模型进行数值模拟,研究转捩对动态失速性能的影响和动态失速下的转捩规律。结果表明,使用考虑转捩效应,能够使动态失速过程中上仰段大迎角状态下失速和下俯段气流再附的模拟得到改善。在动态失速上仰段,上表面转捩由后缘分离泡向前缘分离泡的转变过程较快,导致转捩点迅速前移;而在下俯段,前缘分离泡向后缘分离泡的转变过程中经过了自然转捩和再层流化的过渡,因此转捩点的移动较上仰段平滑。     

尾缘气动弹片对翼型动态失速特性影响研究

通过研究尾缘气动弹片对翼型动态失速特性影响,提出一种基于气动弹片的主动控制策略,使其于大攻角时抬起,小攻角时闭合。并采用计算流体动力学方法对比分析主动式气动弹片对不同厚度翼型抑制流动分离作用的效果。结果表明：对于薄翼型,发生动态失速时,气动弹片可延缓翼型尾缘涡旋与前缘主流涡的相互作用,减小翼型升力系数骤降幅度;随翼型厚度增加,流动分离点从翼型前缘转向后缘,气动弹片可有效分割较大分离涡,减轻流动分离程度,限制分离涡发展,同时抑制尾缘伴随小涡产生,提高翼型升阻比。     

前缘改形对风力机翼型气动性能影响的数值研究

基于翼型参数化方法对翼型S809进行4类不同的前缘修改,分别为前缘压力面加厚、前缘吸力面加厚、前缘上弯和前缘下弯,采用翼型设计分析软件Xfoil和商用CFD(Computational Fluid Dynamics)软件FLUENT分别对翼型气动参数和翼型周围流场进行计算。结果表明:翼型气动特性与流场特性受翼型压力面外形变化影响较小;在研究范围内,翼型吸力面加厚使得翼型在失速区升力系数增加,阻力系数减小;翼型前缘上弯使得翼型在大攻角工况下升力系数减小,阻力系数增大,且使翼型提前失速;在一定范围内翼型前缘下弯,使得翼型升力系数增大,阻力系数减小,且延迟失速。     

翼型前缘对风力机翼型气动性能的影响

基于翼型参数化方法对翼型S809进行两类不同的前缘修改,采用翼型设计分析软件Xfoil对修改前、后的翼型进行气动性能计算分析,并采用计算流体力学（CFD）数值模拟方法进行流场特性分析。结果表明：翼型前缘下弯使得翼型在失速区升力系数增大,阻力系数减小,俯仰力矩系数减小,转捩现象延迟,翼型前缘上弯对气动性能的影响与之相反;翼型前缘上弯和下弯使得翼型表面压力系数分布均匀,吸力面及压力面压力系数增大;翼型前缘下弯能够抑制流动分离,抑制涡的形成,延迟翼型失速,翼型前缘上弯对翼型流场特性的影响则与之相反。     

凹槽-襟翼对翼型动态失速特性影响研究

风力机复杂运行环境使叶片常处于失速环境,导致翼型升力骤降,严重影响风力机气动性能.为改善翼型流动分离,延缓失速,对凹槽-襟翼对翼型动态失速特性作用效果开展研究,并利用计算流体力学方法分析不同折合频率与翼型厚度时凹槽-襟翼对翼型气动性能的影响.结果表明:俯仰振荡过程中,凹槽-襟翼可有效提升翼型吸力面流速,降低失速攻角下逆...     

Insight into wind turbine stall and post‐stall aerodynamics

The objective of this study was to evaluate measured NASA Ames Unsteady Aerodynamic Experiment post‐stall blade element data and to provide guidelines for developing an empirical approach that predicts post‐stall aerofoil characteristics. Blade element data were analysed from the five radial stations of the baseline 5·03 m radius rotor. A lifting surface/prescribed wake performance prediction method was used to determine a reference angle of attack that corresponds to the measured blade element data. Using the measured normal and tangential force coefficients and estimated angle of attack, spanwise distributions of lift and drag performance characteristics were derived along with the circulation distributions. Guidelines for a new stall and post‐stall model based on the measured trends in the aerofoil performance characteristics, along with flat plate theory, are proposed for predicting the peak and post‐peak power. Copyright © 2004 John Wiley & Sons, Ltd.     

The effect of a leading edge erosion shield on the aerodynamic performance of a wind turbine blade

Armour EDGE is a novel shield developed to protect the leading edge of wind turbine blades from erosion. The aerodynamic impact on aerofoils of National Renewable Energy Laboratory (NREL) 5MW wind turbine has been investigated using 2D fully turbulent computational fluid dynamics (CFD), with three profiles at critical locations along the blade simulated both with and without the shield to compare aerodynamic performance. Two wind speeds were investigated that reflect regular operating conditions: at rated speed of 11.4 m/s and a below rated speed of 7 m/s. The results showed that the presence of the shield during rated wind speed reduced the drag by as much as 4.5%, where the lift‐to‐drag ratio increased by a maximum of 4%. At the below rated wind speeds, the shield had negligible impact on the performance of all but one National Advisory Committee for Aeronautics (NACA) 64‐618 profile, which resulted in an increase in the drag coefficient of 7%. It was also found that the suction side of the aerofoil is much more sensitive to leading edge protection placement than the pressure side. It was concluded that the erosion shield as a method of leading edge protection, with a gradual transition from shield to blade, will not have a major impact on the aerodynamic performance of a multi‐megawatt wind turbine blade and could slightly increase aerofoil efficiency at high wind speeds.     

A vortex panel model for the simulation of the wake flow past a vertical axis wind turbine in dynamic stall

A 2D vortex panel model with a viscous boundary layer formulation has been developed for the numerical simulation of a vertical axis wind turbine (VAWT), including the operation in dynamic stall. The model uses the ‘double wake’ concept to reproduce the main features of the unsteady separated flow, including the formation and shedding of strong vortical structures and the wake–blade interaction. The potential flow equations are solved together with the integral boundary layer equations by using a semi‐inverse iterative algorithm. A new criterion for the reattachment of the boundary layer during the downstroke of a dynamically stalled aerofoil is implemented. The model has been validated against experimental data of steady aerofoils and pitching aerofoils in dynamic stall at high and low Reynolds numbers (Re = 1.5 × 10⁶ and Re = 5 × 10⁴). For the low Reynolds number case, time‐resolved 2D particle image velocimetry (PIV) measurements have been performed on a pitching NACA 0012 aerofoil in dynamic stall. The PIV vorticity fields past the oscillating aerofoil are used to test the model capability of capturing the formation, growth and release of the strong leading edge vortex that characterizes the dynamic stall. Furthermore, the forces extracted from the PIV velocity fields are compared with the predicted ones for a quantitative validation of the model. Finally, the model is applied to the computation of the wake flow past a VAWT in dynamic stall; the predicted vorticity fields and forces are in good agreement with phase‐locked PIV data and CFD‐DES available in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

不同相对厚度前缘缝翼对S809翼型气动性能的影响

文章通过数值模拟方法研究了不同相对厚度的前缘缝翼对S809翼型气动性能的影响,并揭示了前缘缝翼相对厚度对流动控制产生影响的机理。研究结果表明:在大攻角下,空气流经过前缘缝翼会在其尾部产生涡旋,尾缘涡旋的形成有助于抑制S809翼型流动分离,进而改善翼型绕流场;不同相对厚度的前缘缝翼产生尾缘涡旋不同的流动轨迹,对翼型的流动控制作用效果不同;相同条件下,前缘安装最大相对厚度为35%的前缘缝翼能够将S809翼型最大升力系数提升至1.25,失速攻角推迟至17.21°;安装最大相对厚度为14%的前缘缝翼,能够使S809翼型最大升力系数提升至1.53,并使翼型在攻角为20.16°时仍未发生失速。     

翼型的选择对轴流泵抗汽蚀性能的影响

先对NACA0010系列的5种最大相对厚度位置不同的翼型分别在GAMBIT中进行轴流泵建模，通过FLUENT软件对5个泵内部流场进行三维数值计算，通过对比分析得出，翼型最大相对厚度在弦长的50％处时对汽蚀的抑制效果最好。再选择最大相对厚度在弦长50％，最大相对厚度不同的4种翼型，对4台泵进行同样的计算，可以得出最大相对厚度为14％时泵的抗汽蚀效果最好。     

Aerodynamic effects of leading‐edge tape on aerofoils at low Reynolds numbers

A systematic wind tunnel study was conducted to gain an understanding of the aerodynamic effects of leading‐edge tape, which is typically used on small wind turbines as a protection from blade erosion. The wind tunnel tests included lift and drag measurements over the Reynolds number range from 150,000 to 500,000. In addition, flow visualization experiments were carried out. Various tape configurations were tested on five aerofoils, namely the BW‐3, FX 63‐137, S822, SG6042 and SG6051. Although the magnitude of the aerodynamic effects of the tape was aerofoil‐dependent, it was found that extending the tape beyond 5% chord and staggering multiple tape layers were most beneficial in minimizing the loss in aerofoil performance. The practical significance of the results on wind turbine performance is discussed. In particular, the data for the SG6042 aerofoil were used to quantify the effects of the tape on the power coefficient of small variable‐speed wind turbines. Overall, the different tape configurations tested reduced the power coefficient by no more than 2·1%. From the trends shown, however, larger reductions in power coefficient should be expected for larger wind turbines than those considered, particularly if two layers of tape are used. In light of this study, guidelines for optimum application are suggested. Copyright © 1999 John Wiley & Sons, Ltd.     

风力机翼型尾缘厚度对粗糙敏感性影响的研究

综合应用涡面元和RANS方法,研究DU93-W-210、DU91-W2-250及DU97-W-300这3种常用翼型经尾缘修型后尾缘厚度对粗糙敏感性的影响.在涡面元方法中采用设置固定转捩和在RANS方法中采用设置锯齿形边界条件的方式来模拟翼型前缘污染,研究发现前缘污染造成翼型吸力峰降低,引起翼型气动性能下降,然而随着尾缘...     

水平轴风力机翼型大攻角分离流动的数值模拟

翼型的失速特性是失调速节型水风力机的气动性能分析和颤振分析的基础，许多涉及这类问题的研究大多只给出了翼型刚开始失速时的计算结果，然而在正常运行工况下叶片端部翼型的深失速特性是风力机的最关键的一类问题，通过求解二维非常，可压的Ｎ－Ｓ方程计算了风力机常用翼型ＮＡＣＡ４４１８的绕流特性，Ｎ－Ｓ方程在贴体坐标系中给出用Ｐｏｉｓｓｏｎ方程法生成了Ｃ型网格，数值计算了采用了一种改进的ＬＵ－ＳＧＳ格式。将翼型的     

V型沟槽对钝尾缘翼型流场分布及气动性能影响的研究

基于k-ωSST湍流模型,利用商业CFD工具ANSYS Fluent 16.0对DU35-17原始翼型、钝尾缘修型翼型及布置V型沟槽钝尾缘翼型进行数值模拟计算,对翼型改进前后的升阻力系数、流场分布和表面压力系数进行对比分析.结果表明,翼型在钝尾缘修型的同时布置V型沟槽,通过改变翼型尾缘处的压力分布和翼型表面的流动分布,...     

尾缘襟翼对风力机翼型气动特性影响研究

尾缘襟翼(TEF)因其对翼型气动特性的调控能力,被认为是降低叶片疲劳和局部载荷最具可行性的气动控制部件。对TEF进行建模,采用Xfoil和CFD软件分析了TEF对翼型气动特性的影响及其机理,并从叶素理论角度对变化来流下TEF的减载效果进行了验证,结果表明:TEF位于不同摆角时翼型升阻力系数均有不同程度的变化,TEF可有效实现对翼型气动特性的主动控制;TEF摆动改变了翼型表面的静压分布和流动状态,进而对翼型升阻力和失速攻角产生影响;TEF可快速有效降低风速突然增加后的叶素受力,进而控制并减小叶片载荷。     

High Reynolds number unsteadiness assessment using 3D and 2D computational fluid dynamics simulations of a thick aerofoil equipped with a spoiler

An operating 2-MW wind turbine has been scanned and analysed using 2D computational fluid dynamics (CFD) and blade element momentum (BEM) analysis. The current work illustrates using full-scale 3D CFD simulations the differences between 2D and 3D simulations and its impact on the local aerofoil vortex shedding frequency. The outcome shows that despite a pressure redistribution and lift change introduced by the blade span and rotation, the vortex shedding frequency remains similar between 2D and 3D thereby validating the novel fatigue calculation method previously proposed.     

Integrating a new flow separation model and the effects of the vortex shedding for improved dynamic stall predictions using the Beddoes–Leishman method

This paper aims at improving dynamic stall predictions on the S809 aerofoil under 2D flow conditions. The method is based on the well‐known Beddoes–Leishman model; however, a new flow separation model and a noise generator are integrated to improve the predictions in the load fluctuations, including those induced by vortex shedding on the aerofoil upper surface. The flow separation model was derived from a unique approach based on the combined use of unsteady aerodynamic loads measurements, the Beddoes–Leishman model and a trial‐and‐error technique. The new flow separation model and random noise generator were integrated in the Beddoes–Leishman model through a new solution algorithm. The numerical predictions of the unsteady lift and drag coefficients were then compared with the Ohio State University measurements for the oscillating S809 aerofoil at several reduced frequencies and angles of attack. The results using the proposed models showed improved correlation with the experimental data. Hysteresis loops for the aerodynamic coefficients are in good agreement with measurements. Copyright © 2016 John Wiley & Sons, Ltd.     

风力机翼型等速上仰动态失速数值模拟

采用κ-ωSST模型,利用CFD软件模拟了NREL S809翼型正弦振荡动态失速,并将结果和俄亥俄州立大学（OSU）风洞试验值对比,显示出较好的一致性,验证了所用方法的有效性．在此基础上对该翼型在雷诺数Re=1．0×10^6时以攻角变化率α=34．54（＊）·s^-1等速上仰动态失速过程进行了数值模拟,详细描述了等速上仰动态失速过程涡的发展以及翼型周围流场的分布．结果表明,动态失速现象是由前缘主涡和尾缘逆向涡交替作用引起;其气动特性曲线的分析结果表明,其失速前气动性能较静态时有较大提升．     

A simple model for deep dynamic stall conditions

The present study is focused on modeling of dynamic stall behavior of a pitching airfoil. The deep stall regime is in particular considered. A model is proposed, which has a low implementation and computational complexity but yet is able to deal with different types of dynamic stall conditions, including those characterized by multiple vortex shedding at the airfoil leading edge. The proposed model is appraised against an extensive data set of experimental (α,C_L) curves for NACA0012. The results of an existing widely used model, having comparable complexity, are also shown for comparison. The proposed model is able to well reproduce not only the classic curves of deep dynamic stall but also the curves characterized by lift oscillations at high angles of attack due to the shedding of multiple vortices. Furthermore, the model appears to be robust to variations of its parameters from the optimal values and of the airfoil geometry. Finally, the model is successfully implemented in a commercial CFD software and applied to the simulation of a vertical axis wind turbine within the actuator cylinder approach. The accuracy of the prediction of the turbine power coefficient in the whole rotation cycle is very good for the optimal working condition of the turbine, for which the model parameters were calibrated. Fairly good accuracy is also obtained in significantly different working conditions without any further calibration.     

定常吸气对垂直轴风力机性能影响研究

定常吸气装置可有效提高垂直轴风力机气动性能,改善风轮流场结构及翼型动态失速特性.基于CFD方法对垂直轴风力机进行数值模拟,研究不同叶尖速比(TSR)下定常吸气对风力机气动及流场特性的影响,对比分析原始风力机及定常吸气作用下的风能利用率、整机转矩系数及涡量分布.结果表明:不同尖速比下定常吸气均可显著提高风力机气动性能,减...